In our current, modern society, radios are an everyday, common tech, wherever they might be, car, home, or even phones. I don’t think you will be able to find anyone in the world today, who doesn’t know about radio. But before the 19^th century, wireless radio communication in everyday life was a thing of pure fantasy. It took many years before radios went mainstream, become a household fixture even after the development of radio in the late 1800s.

Now, there is some debate as to who actually invented the radio. The invention of radio communication spanned over many decades – of experimental investigation of radio waves, engineering and technical developments, establishment of theroretical underpinnings and adaptation to signalling. The various components to make a radio transmission possible, contributed over the years by various great minds, which culminated in a commercially successful wireless communication system by Marconi – awarded the very first wireless telegraphy patent in England in the year 1896, securing his spot in radio’s history as the father of radio.

A Brief history leading up to Radio

So the story of radio began in 1780 or so with George Adams noticing sparks between charged and uncharged conductors when a Leyden jar was discharged. A Leyden jar is an electrical component which stores a high-voltage electric charge between electrical conductors on the inside and outside of a glass jar. But lets jump ahead to Michael Faraday.

In 1831 Michael Faraday began a series of experiments in which he discovered electromagnetic induction. This relation was mathematically modelled by Faraday’s law. Now, Faraday’s law of induction is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force – this phenomenon is known as electromagnetic induction. Why is it important – because it is the fundamental operating principle of transformers, inductors and many types of electrical motors, generators and solenoids.

In 1842 Joseph Henry showed the oscillatory nature of the discharge in leyden jars – how a generated spark could magnetize a needle surrounded by a coil up to 220 feet away. In his published results he also described how a lightning strike 8 miles away magnetized a needle surrounded by a coil, he considered both of these effects to be due to electromagnetic induction at the time however it was most probably caused by radio waves.

In 1864 James Clerk Maxwell predicts the existence of electromagnetic waves in his paper, ‘a dynamic theory of electromagnetic field.’

In 1875 Thomas Edison noticed an electromagnet producing unusual sparks. He found that this spark could be conducted 25 miles along telegraph wires and be detected a few feet from the wire. To prove it was not electromagnetic induction he set up an experiment where he shows sparks in a spark detector but no effect in a gold-leaf electroscope and a galvanometer along the same line. On 28 November 1875 he announces to the press what he terms a new “etheric force”. This is a term Edison coined to describe a phenomenon later understood as high frequency electromagnetic waves – effectively radio.

In 1878, David E. Hughes noticed that sparks generated by an induction balance causes noise in an improved telephone microphone he was developing. He rigged up a portable version of his receiver and, carrying it down a street, found that the sparking could be detected at some distance.

In 1884, Keil Heinrich Hertz produced an analysis of Maxwell’s equations showing they did have more validity than the prevalent action at a distance theories. In physics, action at a distance is the concept that an object can be moved, changed, or otherwise affected without being physically touched (as in mechanical contact) by another object. That is, it is the non-local interaction of objects that are separated in space.

However from 1886-1888, after he noticed how discharging an electric current into a coil produced a spark in a second nearby coil, Heinrich Hertz saw a way to build a test apparatus. He conducted a series of experiments that validated Maxwell’s theory of electromagnetic radiation and proved that it can travel through free space, radio waves. He demonstrated the radiation had the properties of visible light, the properties of waves which are now called transverse waves, and discovered that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation.

In 1893, Nikola Tesla, delivered a lecture, On Light and Other high frequency phenomenon before the Franklin Institute in Philadelphia and the National Electric Light Association in St Louis. Tesla did not think air-born radio waves existed, or even if they did they would probably only travel in straight lines making them useless for long range transmission and instead proposed a wireless lighting and wireless electric power transmission system that would work on air and ground conduction that he also thought could carry messages.

In 1894, Oliver Lodge delivered a lecture on Hertz where he demonstrated the optical properties of Hertzian waves or radio waves, including transmitting them over a short distance, he also demonstrated controlling frequency by changing inductance and capacitance in his circuits.

Towards the end of that same year. Guglielmo Marconi conducted experiments in pursuit of building a wireless telegraph system based on Hertzian waves, a radio transmitter and receiver set up, which he demonstrated at that time to his mother. It made a bell ring on the other side of the room by pushing telegraphic button on the bench. Over the next year, he worked on adapting experimental equipment into a radio wave telegraphic transmitter and receiver system that could work over long distances. That’s considered to be the first development of a radio system, specifically for communication.

And that changed the world of communication as we know it.

Sources:

The Early History of Radio: From Faraday to Marconi by G.R.M Garratt, T.B.A. Senior, John L. Volakis

Wireless Telegraphic Communication – a Nobel Lecture 1909 by Marconi

Titanic’s Wireless Connection by Wireless History Foundation (wirelesshistoryfoundation.org)

Radio waves and the Electromagnetic Spectrum (Radio JOVE Educational material)

Milestones in Radio Technology (www.electronic-notes.com)

Radio Broadcasting by Christopher H. Sterling (Britannica)

On Light and Other High Frequency by Nikola Tesla

Among many other sources.